It is conventional to provide undercarriage track rollers and bogies with suspension elements to absorb shock and improve weight distribution as exemplified in U.S. Pat. No. 7,025,429 (see FIG. 5). As illustrated in FIG. 5, one end of the track frame 1 is provided with a yoke 1a to a distal end of which a track idler 2 is rotatably mounted. A sprocket wheel 3 is rotatably mounted on a vehicle body (not shown) in the vicinity of an opposite end portion of the track frame 1. A plurality of track rollers 11, 12, 43, and 47 are attached in individually rocking manners to a lower portion of the track frame 1 between the idler 2 and the sprocket 3. An endless track chain 6 is trained about the idler 2, sprocket 3 and track rollers 11, 12, 43, and 47. Below the track frame 1 at a location adjacent the idler 2 is a roller unit 40a including an arm 41 having a forward end portion attached to the track frame 1 for rocking vertically about a pin 42. On abutment portions of an upper portion of the arm 41 and a lower location of the track frame 1, respectively, there is mounted elastic members 44a and 44b which abut against each other to restrict upward movement of the arm 41 and to bear the load applied to the track roller 43 to absorb the impact, which might otherwise be received by the track roller 43. Similarly, mounted below the track frame 1 adjacent to sprocket 3 there is a single track roller unit 40b including an arm 45 having its proximal end portion vertically pivotally attached to the lower portion of the track frame 1 for being rocked about a pin 46. Respectively mounted on an upper rear end portion of the arm 45 and a lower portion of the track frame 1 are elastic members 48a and 48b which abut against each other to limit upward pivoting of the arm 45 and to bear the load applied to the track roller 47 to thereby absorb the impact, which might otherwise be received by the track roller 47. In addition, a predetermined number of double track roller units 10 are disposed below the track frame 1 between the track rollers 43 and 47, with each roller unit 10 including a first arm 31 having a proximal end portion attached to the lower portion of the track frame 1 for being rocked vertically on a first pin 33, and a second arm 32 having a central portion mounted to the distal end portion of the first arm 31 for being vertically rocked about a second pin 35. Elastic members 34a and 34b are respectively mounted to the upper portion of the first arm 31 and the lower portion of the frame 1 so that they abut each other and act to restrict upward pivotal movement of the arm 31 and bear the load applied to the lower rollers 11 and 12 to thereby absorb the impact which might otherwise be transferred to the roller 11 and 12. Thus, the roller 43 adjacent the idler 2, the rollers 11 and 12 of the double track roller units 10 and the roller 47 adjacent to the drive sprocket 3 are all suspended. This practice, when extended to track roller adjacent to the drive sprocket, can lead to damage and avoidable wear of the drive sprocket. Further, under load conditions, the rear drive sprocket pulls on the track to propel the crawler in a forward direction, drawing the track taut and, essentially, negating the need for the roller nearest the drive sprocket to be provided with costly suspension.